Edward Thomas is a 0-4-2ST built in 1921 by Kerr, Stuart and Co. Ltd. for use on the Corris Railway.
Edward Thomas worked on the Corris Railway, along with Sir Haydn, until the line's closure in 1948. He was purchased by the Talyllyn Railway in 1951 and named after its former manager. After repairs were carried out by the Hunslet Engine Co., the engine entered service on the Talyllyn in 1952 and has proved most successful. From 1958 until 1969, a Giesl ejector was fitted instead of a conventional chimney, the first such installation in the British Isles.
Following the success of Sir Haydn's stint as Sir Handel between 1982 and 1984, in 1988 it was decided to repaint Edward Thomas into Peter Sam. A ceremony was held on the 14th of May 1988 where the Rev. W. Awdry, acting as the "representative" of Sir Handel Brown, handed over "Peter Sam" to the Talyllyn, supported by his son Christopher Awdry and grandson Richard. "Peter Sam" would spend 12 years on the Talyllyn, during which he became involved in a dispute with The Britt Allcroft Company following the launch of Days Out with Thomas, as Allcroft wanted the Talyllyn to pay licencing fees like other heritage railways. In 1993 an agreement was reached and in 1996 "Peter Sam's" visit to the Talyllyn was featured in New Little Engine. In 2000, Douglas took over as Duncan for Skarloey events, now named "Duncan Days", and Edward Thomas was withdrawn for overhaul.
He was then repainted into the British Railway black, the colour he might have acquired had the Corris line survived a little longer. An extensive overhaul, which included the fitting of a new boiler, was completed in late May 2004, and the engine returned to public service on the thirtieth of that month as "Edward Thomas" in unlined green livery. Following Sir Haydn taking over as main Skarloey engine in 2008, Edward Thomas would occasionally be dressed up as Peter Sam before taking over as main Skarloey engine from Douglas, who reassumed the role in 2013, in 2016, with the events being rebranded as "Peter Sam's Party". Unlike previous times, Edward Thomas was not repainted into Peter Sam's red Railway Series livery and remained in his regular green livery and was only dressed up for the special events. A new face was also made for him.
Edward Thomas is currently running in the standard Talyllyn Railway livery of bronze green with black and yellow lining.
- A book named "Hugh Goes Sliding", written by Christopher Awdry, featured Sir Haydn and Edward Thomas working on the Corris Railway. It was based on a true life event, reminiscent of The Railway Series. It implies that before being purchased by the Talyllyn Railway, Edward Thomas was named "Kerr" after his designer Kerr Stuart. Kerr was also featured in a story for the Corris Railway's newsletter, known as the "Corris-Pondent" alongside Cora.